import java.io.*;
import java.net.*;
import java.util.*;

public final class WebServer {

	public static void main(String argv[]) throws Exception {
		// set the port number
		int port = 1025;
		ServerSocket serverSocket = null;
		// establish the listen socket
		try {
			serverSocket = new ServerSocket(port);
		} catch (IOException e) {
			System.err.println("Could not listen on port: " + port);
			System.exit(1);
		}

		// process htttp service requests indefinitely
		while (true) {
			// listen for TCP connection requests

			// Construct an object to process the HTTP request message.
			HttpRequest request = new HttpRequest(serverSocket.accept());

			// create a new thread to process request
			Thread thread = new Thread(request);

			// start the thread
			thread.start();
		}
	}
}

final class HttpRequest implements Runnable {
	final static String CRLF = "\r\n";
	Socket socket;

	// Constructor
	public HttpRequest(Socket socket) throws Exception {
		this.socket = socket;
	}

	// Implement the run() method of the Runnable interface.
	public void run() {
		try {
			processRequest();
		} catch (Exception e) {
			System.out.println(e);
		}
	}

	private void processRequest() throws Exception {

		// Get a reference to the socket's input and output streams.
		InputStream is = socket.getInputStream();
		// OutputStream os = socket.getOutputStream();
		DataOutputStream os = new DataOutputStream(socket.getOutputStream());

		// Set up input stream filters.
		BufferedReader br = new BufferedReader(new InputStreamReader(is));

		// Get the request line of the HTTP request message.
		String requestLine = br.readLine();

		// Display the request line.
		System.out.println();
		System.out.println(requestLine);

		// Get and display the header lines.
		String headerLine = null;
		while ((headerLine = br.readLine()).length() != 0)
			System.out.println(headerLine);

		// Extract the filename from the request line.
		StringTokenizer tokens = new StringTokenizer(requestLine);
		tokens.nextToken(); // skip over the method, which should be "GET"
		String fileName = tokens.nextToken();

		// Prepend a "." so that file request is within the current
		// directory.
		fileName = "." + fileName;

		// Open the requested file.
		FileInputStream fis = null;
		boolean fileExists = true;
		try {
			fis = new FileInputStream(fileName);
		} catch (FileNotFoundException e) {
			fileExists = false;
		}

		// Construct the response message.
		String statusLine = null;
		String contentTypeLine = null;
		String entityBody = null;
		if (fileExists) {
			statusLine = "HTTP/1.0 200 OK" + CRLF;
			contentTypeLine = "Content-type: " + contentType(fileName) + CRLF;
		} else {
			statusLine = "HTTP/1.0 404 Not Found" + CRLF;
			contentTypeLine = "text/html";
			entityBody = "<HTML>" + "<HEAD><TITLE>Not Found</TITLE></HEAD>"
					+ "<BODY>Not Found</BODY></HTML>";
		}

		// Send the status line.
		os.write(statusLine.getBytes());

		// Send the content type line.
		os.write(contentTypeLine.getBytes());

		// Send a blank line to indicate the end of the header lines.
		os.write(CRLF.getBytes());

		// Send the entity body.
		if (fileExists) {
			sendBytes(fis, os);
			fis.close();
		} else
			os.write(entityBody.getBytes());

		// Close streams and socket.
		os.close();
		br.close();
		socket.close();

	}

	private static void sendBytes(FileInputStream fis, OutputStream os)
			throws Exception {
		// Construct a 1K buffer to hold bytes on their way to the socket.
		byte[] buffer = new byte[1024];
		int bytes = 0;

		// Copy requested file into the socket's output stream.
		while ((bytes = fis.read(buffer)) != -1) {
			os.write(buffer, 0, bytes);
		}
	}

	private static String contentType(String fileName) {
		if (fileName.endsWith(".htm") || fileName.endsWith(".html"))
			return "text/html";
		else if (fileName.endsWith(".jpg") || fileName.endsWith(".jpeg"))
			return "image/jpeg";
		else if (fileName.endsWith(".gif"))
			return "image/gif";

		return "";
	}
}